JPH1134494A - Photothermal conversion material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photothermal conversion material having a photothermal conversion layer of a low cost by improving sensitivity of the conversion layer by raising absorptivity of a laser beam. SOLUTION: The photothermal conversion material comprises a photothermal conversion layer containing laser absorption dye, binder and laminar inorganic compound. The inorganic compound containied in the layer is preferably water swelling synthetic mica, which has an aspect ratio of 100 or more. And, a weight ratio of the mica to the dye and binder in the layer is desirably 1/100 to 55/1000. The material is particularly suitably used for thermal transfer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photothermal conversion material, and more particularly, to a material for performing thermal recording or the like by converting light energy by laser light into heat energy, in particular, a digital color proof in the field of printing.
The present invention relates to a photothermal conversion material suitable for digital printing plates and the like.

[0002]

2. Description of the Related Art In the field of graphic arts, a set of color separation films is output from a color original by a lithographic film, and printing plates are printed using the output films. Generally, a color proof is created, and an error check in a color separation process, a necessity check of color correction, and the like are generally performed. As a material for the color proof, it is considered that a pigment is preferably used as a coloring material together with the image formation on the actual printing paper in view of the similarity with a printed matter.

Further, in recent years, there has been a demand for a dry-type proofing method which does not use a developing solution together with high resolution and high process stability enabling high reproducibility of a halftone image. In addition, with the recent widespread use of digitization systems in the pre-printing process (prepress field), there is an increasing demand for materials for directly producing color proofs from digital signals.

In order to obtain a high-quality color proof,
Generally, it is necessary to reproduce a halftone image of 150 lines / inch or more. For that purpose, a laser beam that can be modulated with a digital signal and that can narrow down the recording light to be used to record a high quality halftone dot from the digital signal is used.

As a method of forming a multicolor image using such a laser beam, a thermal transfer layer containing a layer that absorbs the laser beam and converts it into heat (photothermal conversion layer), a coloring material, a polymer binder, and the like is provided on a support. There is known a method of forming an image by using a material in which a mold image forming layer is provided in this order and attaching and transferring the image forming layer to an image receiving body by heat generated by absorption of laser light.

In such an image forming method, Japanese Patent Application Laid-Open
JP-A-3-319191 describes various compounds as light-to-heat conversion dyes suitable for laser heat transfer to a light-to-heat conversion layer. However, since the power of the laser is generally small, a material capable of efficiently performing photothermal conversion and recording from the material side is required.

As a light-to-heat conversion material capable of efficient light-to-heat conversion and transfer, for example, a light-to-heat conversion layer in which carbon black is dispersed in a binder is known. However, the light-to-heat conversion material having such a light-to-heat conversion layer has a problem in that the image receiving sheet or the like is discolored due to scattering of carbon black during thermal transfer.

In some cases, a photothermal conversion layer using a metal deposited film of Sn, Bi, Te, Sb or the like is used. However, in the case of the thermal transfer sheet having this light-to-heat conversion layer, there is a problem that the reflectance of the laser light is high and the sensitivity of the light-to-heat conversion layer is reduced, and fogging is liable to occur due to the transfer of the metal deposition layer. In general, forming a metal vapor-deposited film requires large-scale equipment such as a vacuum vapor-deposition device, which tends to increase the manufacturing cost. In the case of a light-to-heat conversion layer having an infrared absorbing dye,
In order to achieve the same laser light absorptance as metal, it is necessary to increase the film thickness compared to metal.
The sensitivity decreases.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photothermal conversion material having a photothermal conversion layer capable of improving the sensitivity of the photothermal conversion layer by increasing the absorptance of laser light and reducing the cost. Is to provide.

[0010]

The above object is achieved by a photothermal conversion material having a photothermal conversion layer containing a laser absorbing dye and a binder and a layered inorganic compound. The layered inorganic compound is preferably water-swellable synthetic mica, and the water-swellable synthetic mica preferably has an aspect ratio of 100 or more. The weight ratio of the water-swellable synthetic mica to the laser dye and the binder in the light-to-heat conversion layer is from 1/100 to 55/10
00 is desirable. This light-to-heat conversion material is particularly suitably used for a thermal transfer material.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION When the light-to-heat conversion material of the present invention is used as a heat transfer sheet, the support of the heat transfer sheet has a function of mechanically supporting the light-to-heat conversion layer and the image forming layer. A material having high mechanical strength, heat resistance, and high resistance to organic solvents is preferable. In addition, when light irradiation is performed from the support side, the light transmittance of the support needs to be large with respect to the light wavelength. Further, when using a laser as a light source and narrowing down to a small spot of 10 μm or less, the support It is desirable for the body to have a low birefringence. The thickness of the support may be any of a sheet shape and a plate shape as long as it has the above characteristics, and is used according to the purpose of use. As a general use, a sheet-shaped support is preferably used, and in this case, 5 to 300 μm is used.
m, preferably a thickness of 25 to 150 μm.

The material of the support is generally, for example, polyethylene terephthalate, polycarbonate,
Polyethylene, polyvinyl chloride, polyvinylidene chloride,
High molecular compounds such as polystyrene and styrene-acrylonitrile copolymer can be mentioned, and biaxially stretched polyethylene terephthalate is particularly preferable in terms of mechanical strength and dimensional stability against heat.

The surface of the support may be subjected to a physical surface treatment such as a glow discharge treatment and a corona discharge treatment in order to increase the adhesion to the light-to-heat conversion layer. Further, an undercoat layer may be provided between the support and the light-to-heat conversion layer as needed. As the undercoat layer, a material having a large adhesion between the support and the light-to-heat conversion layer is desirable, and a material having a small thermal conductivity such as polystyrene is used in order to reduce a decrease in sensitivity due to heat conduction of the support. Is preferred. In consideration of these conditions and the resistance of the light-to-heat conversion layer to the coating solvent, a material having a film property is appropriately selected. The thickness is not particularly limited, but is usually preferably 0.01 μm to 2 μm. Also, if necessary, on the side of the support opposite to the light-to-heat conversion layer,
For example, various treatments such as application of an antireflection layer may be performed.

The light-to-heat conversion layer used in the present invention has a function of converting light energy by laser light emitted from a light source into heat energy. It is desirable to use a solid-state laser such as a semiconductor laser and a YAG laser as the laser light. The light-to-heat conversion layer contains at least a laser absorbing dye, a layered inorganic compound, and a binder.
As the laser-absorbing dye, dyes that absorb in the visible to infrared wavelength region, such as cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthraquinone dyes, and pyrylium dyes, are desirable.

The layered inorganic compound in the present invention is preferably a swellable inorganic layered compound. Examples of these compounds include swelling of bentonite, hectorite, saponite, beederite, nontronite, stevensite, beidellite, montmorillonite and the like. Minerals, swellable synthetic mica, swellable synthetic smectite, and the like. These swellable inorganic layered compounds have a laminated structure composed of a unit crystal lattice layer having a thickness of 10 to 15 angstroms, and the substitution of metal atoms in the lattice is significantly larger than other clay minerals. As a result, the lattice layer is deficient in positive charge, and cations such as Na ⁺ , Ca ²⁺ , and Mg ²⁺ are adsorbed between the layers to compensate for this. The cations interposed between these layers are called exchangeable cations and exchange with various cations. In particular, the cations between the layers are Li ⁺ , Na ⁺
In such a case, since the ionic radius is small, the bond between the layered crystal lattices is weak, and the layer swells greatly with water. When shear is applied in this state, it is easily cleaved and forms a stable sol in water. Bentonite and swellable synthetic mica have a strong tendency and are preferred for the purpose of the present invention. Particularly, water-swellable synthetic mica is preferable.

As the water-swellable synthetic mica used in the present invention, Na tetrathick mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ Na or Li teniolite (NaLi) Mg ₂ (Si ₄ O
₁₀₎ F ₂ Na or Li hectorite (NaLi) / 3Mg ₂ / 3L
i _1/3 Si ₄ O ₁₀ ) F _{2 and the} like.

The water-swellable synthetic mica preferably used in the present invention has a thickness of 1 to 50 nm and a plane size of 1 to 20 μm. For diffusion control, the thinner the better, the better, and the planar size is better as long as the smoothness and transparency of the coated surface are not deteriorated. Therefore, the aspect ratio is 100 or more, preferably 200 or more, particularly preferably 500 or more.

In the light-to-heat conversion layer of the present invention, the laser-absorbing dye cations are adsorbed on the cleavage surface of mica, and these laser-absorbing dyes have a regular arrangement in the light-to-heat conversion layer. It is thought that the sensitivity of the light-to-heat conversion layer is improved because light energy can be efficiently converted to heat energy.

When a laser light absorbing dye is used,
These generally have low film strength, that is, low cohesion,
A binder is used in the light-to-heat conversion layer in order to perform development by a peeling method. Such binders include gelatin,
A hydrophilic polymer such as polyvinyl alcohol, polystyrene, acryl, and other hydrophobic polymers can be used, but a hydrophilic polymer is desirable for swelling, cleaving, and dispersing a layered inorganic compound, particularly water-swellable synthetic mica.

The content of the water-swellable synthetic mica in the photothermal conversion layer is such that the weight ratio of mica / laser absorbing dye + binder is 1/100 to 55/100, more preferably 5/100 to 30/100. It is desirable to be within the range. When the content of the water-swellable synthetic mica is less than 1/100, the effect of improving the sensitivity in the light-to-heat conversion layer is small, and when it is more than 55/100, cracks in the light-to-heat conversion layer are likely to occur. The weight ratio of the laser absorbing dye / binder in the light-to-heat conversion layer is 1/10 to 3/1,
More preferably, it is desirable to be in the range of 1/3 to 2/1. When the content of the laser absorption dye is less than 1/10, the effect of improving the sensitivity of the photothermal conversion layer is small, and
When the ratio is more than 1, the laser absorption dye is thermally transferred at the time of thermal transfer, and color mixing is likely to occur.

The thickness of the light-to-heat conversion layer is 0.03 to 1.0 μm.
m, preferably 0.05 to 0.5 μm. In the present invention, the sensitivity of the light-to-heat conversion layer is improved, so that the light-to-heat conversion layer can be made thinner, and the cost can be reduced from this aspect.

The light-to-heat conversion layer can be provided on the support by a known method. That is, a laser-absorbing dye, a layered inorganic compound such as a water-swellable synthetic mica, a binder and the like are sufficiently dissolved and dispersed in an organic solvent and ion-exchanged water, and a wheyer, a spin coating method such as a spinner, gravure, The coating is performed by a web coating method using a doctor blade or the like, or a dip coating method. As the organic solvent, alcohols, ketones, cellosolve acetate and the like are suitable.

In the present invention, in the case of a thermal transfer sheet, the above-mentioned light-to-heat conversion layer is provided on a support, and an image forming layer is provided on this light-to-heat conversion layer. As a material for the image forming layer, a mixture of a coloring material and a binder is preferably used for visualizing an image. Pigments and dyes are used as coloring materials. Pigments are generally classified into organic pigments and inorganic pigments. The former has excellent transparency of a coating film, and the latter generally has excellent concealing properties.

When used for printing color proofing, organic pigments having a color tone that matches or approximates yellow, magenta, cyan, and black used in printing inks are preferably used. In addition, metal powders and fluorescent pigments are used according to the purpose. Pigments suitably used include azo-based, phthalocyanine-based, anthraquinone-based, etc., sulene-based, dioxazine-based, quinacridone-based, and isoindoline-based pigments.

The image forming layer contains at least one binder to control its film properties and brittleness. Binders are also used to control the rheological properties of the coatings and to stabilize the pigments in the dispersion. Typically, the pigment and the binder or a portion of the binder are milled in a mill until the desired particle size is obtained.

The ground paste is diluted with a solvent or solvent mixture to obtain a dispersion of the desired viscosity. In order to selectively transfer the image forming layer corresponding to the image-irradiated portion and the non-irradiated portion and obtain a high-quality image, both the shear breaking force and the elongation of the image forming layer coating film used in the present invention are small. Is preferred. For that purpose, it is desirable that at least one of the binders suitable for the image forming layer is brittle at the peeling development temperature. From this viewpoint, when at least one of the binders is a polymer having a glass transition temperature Tg, the glass transition temperature Tg is preferably at least room temperature.

The image forming layer is brittle together with the pigment and the binder, and has good characteristics in obtaining a high quality image of only one color. However, another image is formed on the image already formed on the image receiving body. In the case of recording, transferring, bonding and multi-coloring, strong pressurizing or heating conditions are required, and the recording apparatus is complicated and tends to be expensive. In such a case, the adhesion and cohesion of the coating can be controlled by adding a plasticizer to the image forming layer. The image forming layer may contain a surfactant, a thickener, a dispersion stabilizer, an adhesion promoter, and other additives.

As the image receiving sheet used for the thermal transfer sheet in the present invention, any known image receiving sheet can be used. However, in terms of performance such as image quality and recording sensitivity, an image receiving layer mainly comprising a polymer is provided on a support. The structure provided with is desirable. As such an image receiving sheet, there are two types: a case where a recorded image is used as it is as a final image, and an intermediate image receiving sheet for retransferring a formed image to another image receiving body for use. In this case, the support or the intermediate layer between the image receiving layer and the support preferably has a cushioning property. Such an image receiving sheet is disclosed in JP-A-61-18.
The image receiving sheet described in JP-A No. 9535 and JP-A-9-71059 can be suitably used.

It is needless to say that the photothermal conversion material of the present invention can be used in fields such as image recording by converting light energy into heat energy in addition to the above-described photothermal transfer sheet. Such a field can be used in many fields for recording using heat. For example, specifically describing a printing plate, a material having a structure in which a laser-absorbing ablation layer and a silicone resin layer are laminated on an aluminum substrate is receiving attention for digital on-demand printing. By irradiating the above material with a high-power laser to cause ablation due to the thermal decomposition reaction of the laser absorption layer (light-to-heat conversion layer), and then removing the silicone resin layer (ink repellency) with the treatment liquid, the ink adhesion (Resilience) This is a method of forming and printing an image. The photothermal conversion material of the present invention can be used for the photothermal conversion ablation layer of this material.

The material obtained by coating and laminating the light-to-heat conversion material of the present invention on a transparent plastic substrate (for example, a polycarbonate substrate) is a material in which the light-to-heat conversion material layer itself is melted, thermally decomposed, etc. by the thermal action of laser light. Since the data is recorded by the action of (1) and causes a change in the light reflectance, it can be applied to uses such as optical disks and optical cards. Further, in the case of a thermosensitive coloring recording paper, the coloring of the dye precursor is caused by using heat converted from laser light, and is common to the laser thermal transfer in that only heat converted from light is used. .

[0031]

EXAMPLES Example 1 (Preparation of Light-to-Heat Conversion Layer) The following coating liquid for a light-to-heat conversion layer was prepared. Infrared absorbing cyanine dye (Structural formula 1 below) 0.3 parts by weight Synthetic mica 0.1 parts by weight (Suzulite 40H, MRI (MRI)) Polyvinyl alcohol 6 parts by weight (Poval, Type 205, Kuraray Co., Ltd.) 5 parts by weight of isopropyl alcohol 20 parts by weight of ion-exchanged water The above components were mixed with stirring with a stirrer to prepare a coating solution for a photothermal conversion layer.

Structural formula 1

Embedded image

Preparation of Support A film having a styrene-butadiene copolymer (thickness 0.5 μm) and gelatin (thickness 0.1 μm) provided in this order as an undercoat layer on a 75 μm thick polyester terephthalate was prepared. And a support for a thermal transfer sheet.

On the support, the above-mentioned coating solution for a light-to-heat conversion layer was applied for 1 minute using a rotary coating machine (Wheyer), and the coated product was dried in an oven at 100 ° C. for 2 minutes.
A light-to-heat conversion layer was formed. When the cross section of this photothermal conversion layer was observed with a scanning electron microscope, the average film thickness was 0.25 μm.
Met. The absorbance at 830 nm measured by a spectrophotometer was 1.6.

Comparative Example 1 A light-to-heat conversion layer was prepared in the same manner as in Example 1, except that mica was not used in the coating solution for the light-to-heat conversion layer. When the cross section of this light-to-heat conversion layer was observed with a scanning electron microscope, the average film thickness was 0.3 μm. Further, the absorbance at 830 nm measured by a spectrophotometer was 1.4.

Example 2 An image forming layer was provided on the photothermal conversion layer prepared in Example 1 to prepare a thermal transfer sheet. Preparation of mother liquor for image forming layer coating liquid 63 parts by weight of a 20% by weight solution of polyvinyl butyral (Denka Butyral # 200-L, manufactured by Denki Kagaku Kogyo Co., Ltd.) (solvent: n-propyl alcohol) Color material (magenta pigment, Toyo Ink Co., Ltd.) Company, Lionol Red 6B4290G, CI Pigment Red 57: 1) 12 parts by weight Dispersing aid (manufactured by ICI Corporation, Solsverse S-2,000) 0.8 part by weight n-propyl alcohol 60 parts by weight Glass 100 parts by weight of beads The above components were dispersed for 2 hours using a paint shaker (manufactured by Toyo Seiki Co., Ltd.) to prepare a mother liquor.

Preparation of coating solution for image forming layer 10 parts by weight of mother liquor for coating solution for image forming layer 60 parts by weight of n-propyl alcohol Surfactant (manufactured by Dainippon Ink Co., Ltd., Megafac F-176PF) 0.05 part by weight Part The above components were mixed with a stirrer under stirring to prepare a magenta image forming layer coating solution. A magenta image forming layer coating solution is applied to the light-to-heat conversion layer provided on the thermal transfer sheet support for 1 minute by using a rotary coating machine (Woerr),
The coating was dried in an oven at 100 ° C. for 2 minutes to form an image forming layer. When the cross section of this image forming layer was observed with a scanning electron microscope, the average film thickness was 0.25 μm.

Comparative Example 2 An image forming layer was provided on the light-to-heat conversion layer containing no mica of Comparative Example 1 in the same manner as in Example 1 to prepare a thermal transfer sheet.

(Preparation of Image Receiving Element) Adjustment of Coating Solution for Image Receiving Layer Image Coating Solution for First Receiving Layer Polyvinyl Chloride (ZEON 25, manufactured by Zeon Corporation) 9 parts by weight Surfactant (manufactured by Dainippon Ink Co., Ltd.) , Megafac F-177P) 0.1 parts by weight Methyl ethyl ketone 130 parts by weight Toluene 35 parts by weight Cyclohexane 20 parts by weight Dimethylformamide 20 parts by weight

Coating solution for image receiving second layer Methyl methacrylate / ethyl acrylate / methacrylic acid copolymer (Dianal BR-77, manufactured by Mitsubishi Rayon Co., Ltd.) 17 parts by weight Alkyl acrylate / alkyl methacrylate copolymer (Mitsubishi Rayon Co., Ltd. ), Dianal BR-64) 17 parts by weight Bentaerythritol tetraacrylate (Shin-Nakamura Chemical Co., Ltd., A-TMMT) 22 parts by weight Surfactant (Dainippon Ink Co., Ltd., Megafac F-177P) 0.4 parts by weight Methyl ethyl ketone 100 parts by weight Bidoroquinone monomethyl ether 0.05 part by weight 2,2-dimethoxy-2-phenylacetophenone (photopolymerization initiator) 1.5 parts by weight

Coating of Image Receiving Layer Using a polyester terephthalate (PFT) film having a thickness as a support, the coating solution for the image receiving first layer is applied by using a rotary coater (whiter), and is then placed in an oven at 100 ° C. for 2 minutes. Dried. The thickness of the obtained first layer was 1 μm. An image receiving element was obtained on the first layer by applying the same method using a coating liquid for the second layer and laminating an image receiving second layer having a dry film thickness of 26 μm.

Using the above-described thermal transfer sheet and the image receiving element, laser thermal transfer recording was performed under the following conditions. Semiconductor laser wavelength: 830 μm Beam diameter on the light-to-heat conversion layer: 7 μm Laser power on the film surface: 110 mW Laser scanning: An image receiving element on the outer peripheral surface of a cylindrical drum having a diameter of 20 cm, and a thermal transfer sheet is brought into contact therewith and brought into close contact therewith. Fixed, scanning speed 8m / sec, sub-scanning pitch 5μm

As a result of the test, when the thermal transfer sheet of Comparative Example 2 was used, the line width was 6 μm. On the other hand, when the thermal transfer sheet of Example 2 was used, the line width was 7 μm. As a result, the sensitivity was improved by nearly 20%.

[0044]

As described above, according to the present invention, since the photothermal conversion layer contains the laser absorbing dye and the binder and the layered inorganic compound such as water-swellable synthetic mica, the absorption rate of the laser light is high. The sensitivity of the light-to-heat conversion layer is improved. For this reason, the thickness of the light-to-heat conversion layer can be reduced, or the content of the expensive laser-absorbing dye in the light-to-heat conversion layer can be reduced, so that the cost can be reduced.

Claims (5)

[Claims] 1. A light-to-heat conversion material comprising a light-to-heat conversion layer containing a laser absorbing dye and a binder and a layered inorganic compound. 2. The photothermal conversion material according to claim 1, wherein the layered inorganic compound is water-swellable synthetic mica. 3. The photothermal conversion material according to claim 1, wherein the water-swellable synthetic mica has an aspect ratio of 100 or more. 4. The weight ratio of the water-swellable synthetic mica to the laser dye and the binder is from 1/100 to 55/1.
The photothermal conversion material according to claim 2, wherein the photothermal conversion material is 000. 5. The photothermal conversion material according to claim 1, wherein the photothermal conversion layer is provided on a thermal transfer material.